Power Semiconductor Module Comprising an Explosion Protection System

ABSTRACT

A power semiconductor module for energy distribution, includes at least one power semiconductor, connection terminals for connecting the power semiconductor module, and a housing, in which protection from explosion is ensured in the module even in the event of electric arcs. Therefore, each power semiconductor and each connection terminal is disposed in the housing, and the housing includes an exhaust gas channel for the controlled withdrawal of hot gases and/or plasma in the event of an explosion.

The invention relates to a power semiconductor module for energydistribution comprising at least one power semiconductor, connectionterminals for connection of the power semiconductor module, and ahousing.

Such a power semiconductor module is already known from DE 98 39 422,which discloses an explosion protection system for semiconductormodules, wherein the semiconductor is arranged in a protective sheathingthat captures fragments that are hurled away in the event of anexplosion of the power semiconductor. In this way the intention is toprevent persons or adjacent components from being harmed or damaged bythe explosion. What is disadvantageous about the previously known powersemiconductor component is that the explosion protection system is notsuitable for ensuring a sufficient protection when an arc occurs.

It is an object of the invention, therefore, to provide a powersemiconductor module of the type mentioned in the introduction whichprovides explosion protection including when arcs occur.

The invention achieves this object by virtue of the fact that each powersemiconductor and each connection terminal are arranged in the housing,wherein the housing has an exhaust gas channel for the controlledcarrying away of hot gases and/or plasma in the event of an explosion.

According to the invention, not only the actual power semi-conductor isarranged in a component. Rather, all elements of the power semiconductorelectronics are arranged in the housing, when the housing itself is alsopart of the power semiconductor module. The power semiconductorelectronics comprise for example all the power semiconductors, that isto say all the controllable power semiconductors and theirparallel-connected freewheeling diodes, and also the control units forcontrolling the power semiconductors. Only the free ends of theconnection terminals of the power semiconductor module are led out fromthe housing in order to connect this to further components, for exampleto further power semiconductor modules in accordance with the presentinvention. An arc caused by one of the power semiconductors in the eventof a fault therefore arises within the housing and is shielded towardthe outside by the housing. In order that the explosion forces and thehot gases that arise are carried away toward the outside in a controlledmanner, an exhaust gas channel toward the outside is provided. In thiscase, the exhaust gas channel is guided in such a way, and its openingsare expediently positioned in such a way, that the emerging hot gases orfragments that have been hurled away can damage neither adjacentcomponents nor persons.

Advantageously, the exhaust gas channel is filled with a thermostablefiller through which a flow can pass and which has a large internalsurface area. By means of this preferred further development of theinvention, emerging hot gases or plasma are or is cooled by the fillerprior to emerging from the exhaust gas channel. The cooling is all thegreater, the greater the internal surface area of the filler. The fillerfurthermore holds back accelerated particles formed during an explosionin the event of a fault. Furthermore, pressure relief is provided by thefiller.

In the case of a further development that is expedient in this regard,the thermostable filler is produced for example from a ceramic. In thiscase, the ceramic is expediently formed in such a way that amultiplicity of internal channels and continuous pores are provided init, such that the hot gas or the plasma can still flow through theceramic. Furthermore, the ceramic is temperature-resistant and also ableto withstand the high temperatures that arise during arcing in a mannerfree of damage to the greatest possible extent.

In one preferred variant of the invention, however, the thermostablefiller is a metal foam. Expedient metal foams are commercially availableand can be procured as such without any problems. They have a largeinternal surface area and also a low weight. Furthermore, their thermalcapacity is so high and their temperature resistance is sufficient to beable to withstand the high plasma temperatures in the event of arcing.Furthermore, metal foams are durable, such that particles are held backeffectively and a particularly high pressure relief is furthermoreprovided.

In accordance with a further development that is expedient in thisrespect, the metal foam is an open-pored metal foam. The open pores ofthe metal foam ensure that there is a sufficient capability for the hotgases and plasma to flow through, with the result that an explosion ofthe entire housing is effectively prevented.

In a departure from this, the thermostable filler is a metal wool. Ametal wool forms a so-called chaotic tangle of metal filaments and isalso referred to as a “scouring pad”. Metal wool is often used as aflashback arrestor and can be procured more cost-effectively than metalfoam, for example.

In the context of the invention, the housing can, in principle, compriseany suitable thermostable housing having sufficient mechanical strength.Expediently, however, the housing is a plastic housing or a metalhousing. The plastic of the plastic housing is expediently reinforced byfibers.

The power semiconductors advantageously comprise turn-off powersemiconductors. Turn-off power semiconductors can be transferred by anelectrical control signal from an off-state position, in which a currentflow via the power semiconductor is interrupted, into an on-stateposition, in which the current flow via the turn-off power semiconductoris enabled. In addition, the transfer of the turn-off powersemiconductor from its on-state position into the off-state position canalso be brought about actively by means of a control pulse. Turn-offpower semiconductors are known as such to the person skilled in the artand are commercially available. Examples of turn-off powersemiconductors are IGBTs, IGCTs, GTOs or the like.

In accordance with one preferred exemplary embodiment of the invention,the power semiconductor module has a first connection terminal, a secondconnection terminal, an energy store arranged outside the housing and apower semiconductor branch connected in parallel with the energy store,said power semiconductor branch having two series-connected controllablepower semiconductors, wherein a freewheeling diode that is connected inthe opposite sense is connected in parallel with each controllable powersemiconductor and the junction point of the emitter of a firstcontrollable power semiconductor of the power semiconductor branch andthe anode of the freewheeling diode that is connected in the oppositesense and is assigned to the first controllable power semiconductorforms the first connection terminal and wherein the junction point ofthe controllable power semiconductors of the power semiconductor branchand the freewheeling diodes forms the second connection terminal. Such acircuit has also become known as a Marquardt circuit. The Marquardtcircuit has two switching states, wherein the voltage dropped at theconnection terminals is equal to zero in a first switching state and isequal to the voltage of the energy store in a second switching position.

In a departure from this, the power semiconductor module has a firstconnection terminal, a second connection terminal, an energy store and apower semiconductor branch connected in parallel with the energy store,said power semiconductor branch having two series-connected controllablepower semiconductors, wherein a freewheeling diode that is connected inthe opposite sense is connected in parallel with each controllable powersemiconductor and the junction point of the collector of a firstcontrollable power semiconductor of the power semiconductor branch andthe cathode of the freewheeling diode that is connected in the oppositesense and is assigned to the first controllable power semiconductorforms the first connection terminal and the junction point of thecontrollable power semiconductors of the power semiconductor branch andthe freewheeling diode forms the second connection terminal. This is analternative configuration of the Marquardt circuit, which hasessentially the same properties.

The invention furthermore relates to a converter valve branch comprisinga series circuit formed by power semiconductor modules as claimed in anyof the preceding claims.

Furthermore, the invention relates to a converter comprising a bridgecircuit formed by the converter valve branches mentioned above.

In other words, the invention also relates to converters composed ofseries circuits formed by power semiconductor modules according to theinvention. Such converters are also called multilevel converters. Theyenable the voltages of the individual power semiconductor modules to beturned on and off in a stepwise manner and hence finer and more preciseregulation of the voltage.

Further expedient configurations and advantages of the invention are thesubject matter of the following description of exemplary embodiments ofthe invention with reference to the figures of the drawing, whereinidentical reference symbols refer to identically acting components andwherein

FIG. 1 shows an exemplary embodiment of converter branches according tothe invention

FIG. 2 shows an equivalent circuit diagram of an exemplary embodiment ofa power semiconductor module according to the invention,

FIG. 3 shows an equivalent circuit diagram of an exemplary embodiment ofa power semiconductor module according to the invention, and

FIG. 4 shows an exemplary embodiment of a power semiconductor moduleaccording to the invention without an energy store.

FIG. 1 shows an exemplary embodiment of converter branches 1 accordingto the invention which comprise a series circuit formed by powersemiconductor modules 2. In this case, the converter valve branches 1are arranged in series with one another. The number of powersemiconductor modules 2 within a converter valve branch 1 depends on therespective application, in particular on the required voltages. Thenumber can therefore vary between a few tens up to hundreds of powersemiconductor modules 2.

An AC voltage connection 3 is provided between the converter valvebranches 1 and is provided for connection to a phase of an AC voltagepower supply system. A DC voltage connection 4 is provided at that endof each converter valve branch 1 which is remote from the AC voltageconnection 3. Consequently, each converter valve branch 1 is arrangedbetween an AC voltage connection 3 and a DC voltage connection 4. In thecase of a three-phase AC voltage power supply system to be connectedhere therefore, an exemplary embodiment of a converter according to theinvention would comprise for example six converter valve branchesconnected up to one another in a bridge circuit that is known as such.This can be a so-called six-pulse bridge circuit or alternatively atwelve-pulse bridge circuit.

FIG. 2 shows an equivalent circuit diagram of an exemplary embodiment ofa power semiconductor module 2 according to the invention. It can bediscerned that each power semiconductor module 2 has an energy store inthe form of a capacitor 5. The capacitor 5 is connected in parallel witha power semiconductor branch 6, wherein the power semiconductor branch 6comprises a series circuit formed by two so-called IGBTs 7. Each IGBT 7has a freewheeling diode 8 connected in parallel with it in the oppositesense. The component comprising the controllable power semiconductors 7and the diodes 8 that are connected in the opposite sense together withthe control electronics, is referred to hereinafter as the powerelectronics. The power electronics are connected in parallel with thecapacitor 5. FIG. 2 furthermore reveals a first connection terminal 9and a second connection terminal 10, wherein the first connectionterminal 9 is connected to the emitter of the controllable powersemiconductor 7 and simultaneously to the anode of the diode 8 that isconnected in the opposite sense and is assigned to said powersemiconductor, that is to say in other words to their junction point.The second connection terminal 10 is connected to the junction point ofthe controllable power semiconductors 7 and to the junction point of thediodes 8 that are connected in the opposite sense. If the controllablepower semiconductor 7 arranged between the connection terminals 9 and 10is in its on-state position, the voltage zero is dropped at theconnection terminals 9 and 10. If, by contrast, said power semiconductoris in its off-state position but the controllable power semiconductor 7that is not arranged between the connection terminals 9 and 10 is in itson-state position, the voltage present at the capacitor 5 is droppedbetween the connection terminals 9 and 10.

FIG. 3 shows an alternative configuration of the power semi-conductormodule 2 in accordance with FIG. 2. In contrast to the variant of aMarquardt circuit as shown in FIG. 2, in FIG. 3 the first connectionterminal 9 is connected to the collector of the turn-off powersemiconductor 7 and to the cathode of the freewheeling diode 8 that isconnected in the opposite sense and is in parallel therewith. The secondconnection terminal 10 is connected to the junction point of theturn-off power semiconductors 7 and of the freewheeling diodes 8. Theexemplary embodiments of the Marquardt circuit that are shown in thefigures are equivalent to one another and therefore have the sameproperties.

FIG. 4 shows an exemplary embodiment of the power semiconductor module 2according to the invention. It can be discerned that the powersemiconductor module 2 has not only the controllable powersemiconductors 7 and the connection terminals 9 and 10 but also ahousing 11, which is composed of a metal, such as sheet steel, in theexemplary embodiment shown. Furthermore, two exhaust gas channels 12 areillustrated in the housing 11, said channels being partly open towardthe connection terminals 9 and 10. In the event of an arc occurring inthe housing 10, the hot gases are therefore led toward the outsidethrough the exhaust gas channels 12, wherein the opening of the exhaustgas channels 12 is oriented in such a way that damage to componentsarranged outside the housing 11 can be reliably avoided. A metal foamhaving a large internal surface area is furthermore arranged in theexhaust gas channels 12 for the purpose of cooling the hot gases. Inother words, the metal foam is open-pored, such that the hot gases orother explosion gases can flow through it. In this case, the largesurface area gives rise to a large heat exchange area and to a largetemperature exchange between the metal foam and the emerging hot gases,which are cooled in this way. Furthermore, the metal foam preventsparticles from exiting, wherein pressure relief is additionallyprovided.

1-12. (canceled)
 13. A power semiconductor module for energydistribution, said power semiconductor module comprising: a housinghaving an exhaust gas channel for controlled leading away of hot gasesand/or plasma in the event of an explosion; at least one powersemiconductor disposed in said housing; and connection terminalsdisposed in said housing for connection of the power semiconductormodule.
 14. The power semiconductor module according to claim 13,wherein said exhaust gas channel is filled with a thermostable fillerthrough which a flow can pass and which has a large internal surfacearea.
 15. The power semiconductor module according to claim 14, whereinsaid thermostable filler is produced from ceramic.
 16. The powersemiconductor module according to claim 14, wherein said thermostablefiller is a metal foam.
 17. The power semiconductor module according toclaim 16, wherein said metal foam is an open-pored metal foam.
 18. Thepower semiconductor module according to claim 14, wherein saidthermostable filler is a metal wool.
 19. The power semiconductor moduleaccording to claim 13, wherein said housing is a plastic housing or ametal housing.
 20. The power semiconductor module according to claim 13,wherein said at least one power semiconductor is at least one turn-offpower semiconductor.
 21. The power semiconductor module according toclaim 13, which further comprises: a first connection terminal and asecond connection terminal of said connection terminals; an energystorage device; a power semiconductor branch connected in parallel withsaid energy storage device; said at least one power semiconductorincluding first and second series-connected controllable powersemiconductors of said power semiconductor branch; first and secondreverse-acting freewheeling diodes respectively connected in parallel tosaid first and second controllable power semiconductors; a junctionpoint between an emitter of said first controllable power semiconductorand an anode of said first reverse-acting freewheeling diode connectedto said first controllable power semiconductor, forming said firstconnection terminal; and a junction point between an emitter of saidsecond controllable power semiconductor and an anode of said secondreverse-acting freewheeling diode connected to said second controllablepower semiconductor, forming second connection terminal.
 22. The powersemiconductor module according to claim 13, which further comprises: afirst connection terminal and a second connection terminal of saidconnection terminals; an energy storage device; a power semiconductorbranch connected in parallel with said energy storage device; said atleast one power semiconductor including first and secondseries-connected controllable power semiconductors of said powersemiconductor branch; first and second reverse-acting freewheelingdiodes respectively connected in parallel to said first and secondcontrollable power semiconductors; a junction point between a collectorof said first controllable power semiconductor and a cathode of saidfirst reverse-acting freewheeling diode connected to said firstcontrollable power semiconductor, forming said first connectionterminal; and a junction point between a collector of said secondcontrollable power semiconductor and a cathode of said secondreverse-acting freewheeling diode connected to said second controllablepower semiconductor, forming second connection terminal.
 23. A convertervalve branch, comprising a series circuit of power semiconductor modulesaccording to claim
 13. 24. A converter, comprising a bridge circuitincluding converter valve branches each having a series circuit of powersemiconductor modules according to claim 13.